FILE - Former New York City Mayor Ed Koch (Photo by Jemal Countess/Getty Images for Bryan Cave LLP)

NEW YORK (CBSNewYork) — Ed Koch was placed in intensive care on Thursday.

The 88-year-old former mayor of New York City is battling a build-up of fluid in his lungs and legs, CBS 2’s Dick Brennan reported.

Koch, always a fighter, is battling a lung ailment, and doctors at New York Presbyterian are taking a wait-and-see approach.

“I spoke to the Mayor this morning, and he was feeling discomfort,” Koch spokesman George Arzt said.

Ed Koch Moved To ICU At New York-Presbyterian Hospital

When asked how serious he thinks the former mayor’s condition is, Arzt told 1010 WINS, “We’ll take it day by day.”

“He is not in pain. He did speak to me this morning and told me that he was tired,” Arzt told WCBS 880’s Rich Lamb. “His vital signs are stable. He does have an iron deficiency but the doctors are addressing that.”

Koch has been suffering from fluid in the lungs and legs. He dropped 16 pounds of water from his body during his hospital stay last week, and doctors have ordered him to stop eating salt.

“From what we know he has water on the lungs and that could be from the lung infection he had or the anemia he faced,” Dr. Suzanna Steinbaum said.

Steinbaum of Lenox Hill Hospital said the next 24 to 48 hours are crucial.

“He can recover from this, but he really needs to be monitored very carefully,’ Dr. Steinbaum said.

On Tuesday night, a new documentary about Koch’s career premiered at the Museum of Modern Art. Arzt said Koch asked about how many people attended, and who they were. On Thursday night some famous New Yorkers took time out on the red carpet to wish him well.

“He did a great job and has a very specific personality and I hope he comes home again,” actress Bernadette Peters said.